Hikaru likes watching his older brothers' reactions around Ema. He showed some of his "other" side, where he dressed as a man and watched Ema on top of Azusa.
He is very cunning, being able to provoke reactions from his brothers with only a few simple questions. He has a very sly nature, similar to that of a fox, and is able to get what he wants through harmless manipulation so. He also has something of a slight sadistic shade to him as well, seeing the conflict of his family as a game and keepping statistical track of each brothers chances, including his own. This is further emphasized in season 2 volume 2 (Ch. 27) when he suggests that they all start forcing themselves on Ema and stop being so tame, which earns him a well-deserved punch from Kaname.
Still, in the end, he is a good person who cares about his family, albeit in an unorthodox manner. When cross-dressing, he usually wears a crimson dress with a black jacket, thigh high boots, and tights. [Source: wikia]
You can download this papercraft toy here: Brothers Conflict - Chibi Asahina Hikaru Free Paper Toy Download [Instruction]